This proposal is made to study the primary and tertiary structure of DNA unwinding protein in relation to its functional activities. The initial steps of our research will be, 1) partial sequencing of 32P (DNA unwinding protein, gene 32-protein) of bacteriophage T4 using limited proteolysis and various mutations in gene 32; and 2) to establish a model for the DNA unwinding mechanism. Presently we are proposing the following model. The native 32P molecule has two ends of its peptide chain protruding so that they are within easy access to other proteins. They function as a regulatory control through protein-protein interactions. The role of one end is to localize duplex unwinding to a specific site within the replication fork; 32P acts as unwinding protein in front of the replication fork but acts as renaturation protein elsewhere to avoid uncontrolled unwinding of entire chromosome. The other end of the peptide chain is rleated to 32P-32P interaction through which self-association and cooperative binding to DNA are achieved. We intend either to confirm this model or present an alternative.